U.S. patent number 5,327,108 [Application Number 08/178,350] was granted by the patent office on 1994-07-05 for surface mountable interdigital block filter having zero(s) in transfer function.
This patent grant is currently assigned to Motorola, Inc.. Invention is credited to Truc G. N. Hoang, Darren V. Weninger.
United States Patent |
5,327,108 |
Hoang , et al. |
July 5, 1994 |
**Please see images for:
( Certificate of Correction ) ** |
Surface mountable interdigital block filter having zero(s) in
transfer function
Abstract
Interdigitation and surface mounting of a block filter that has
at least a first resonator and that has at least a first pole and
at least a first zero in its transfer function provides a surface
mountable block filter having selectable frequency rejection
response operation.
Inventors: |
Hoang; Truc G. N. (San Diego,
CA), Weninger; Darren V. (Maize, KS) |
Assignee: |
Motorola, Inc. (Schaumburg,
IL)
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Family
ID: |
27099780 |
Appl.
No.: |
08/178,350 |
Filed: |
January 6, 1994 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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962622 |
Oct 16, 1992 |
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667844 |
Mar 12, 1991 |
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Current U.S.
Class: |
333/203;
333/206 |
Current CPC
Class: |
H01P
1/2056 (20130101) |
Current International
Class: |
H01P
1/205 (20060101); H01P 1/20 (20060101); H01P
001/205 () |
Field of
Search: |
;333/202,203,206,207,222 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0189001 |
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Aug 1986 |
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JP |
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0038601 |
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Feb 1987 |
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JP |
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0154801 |
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Jul 1987 |
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JP |
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0306701 |
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Dec 1988 |
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JP |
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Primary Examiner: Ham; Seungsook
Attorney, Agent or Firm: Stockley; Darleen J.
Parent Case Text
This is a continuation of application Ser. No. 07/962,622, filed
Oct. 16, 1992 and now abandoned which is a continuation of
application Ser. No. 07/667,844, filed Mar. 12, 1991 and now
abandoned.
Claims
We claim:
1. A surface mountable interdigital block filter for filtering
electrical signals, the block filter being substantially directly
mountable on a conductive surface of a substrate, comprising:
a substantially parallelepiped volume of dielectric material having
at least a first and a second surface. substantially arranged to
provide;
at least three primary apertures extending coaxially from said
first and Second surfaces and having conductive material disposed
on an inner surface of said apertures to provide conductive
resonator means,
input and output secondary apertures extending coaxially from said
first and second surfaces and having conductive material disposed
on an inner surface of said secondary apertures to provide
conductive resonator means, for at least facilitating external
conductive connections and at least allowing desired provision and
extraction of electrical signals,
wherein the secondary apertures are operably coupled to the primary
apertures and the apertures are arranged in an order of:
a first primary aperture, the input secondary aperture, a second
primary aperture, any primary apertures selected in addition to the
three primary apertures, the output secondary aperture and a third
primary aperture,
a first conductive line is utilized for input into the input
secondary aperture and a second conductive line is utilized for
output from the output secondary aperture,
wherein adjacent apertures are at least alternately connected and
unconnected to a ground respectively along the first surface and
along the second surface such than said conductive resonator means
are interdigitated; and
conductive material is disposed on at least Dart of the surfaces of
the volume of dielectric material, substantially arranged to at
least permit conductive surface mounting of the surface mountable
interdigital block filter on the conductive surface of the
substrate and to provide an electrical signal filter that provides
for selectable frequency rejection response operation
wherein the input and output secondary apertures are utilized,
respectively, to radiate and receive signals to and from adjacent
conductive interdigitated resonator(s) means,
wherein said conductive interdigitated resonator means are
constructed and arranged such that the block filter has at least a
first pole and at least a first zero in its frequency transfer
function provided by at least a first resonator that is utilized
for zero(s) of a frequency transfer function, and
wherein the input and output secondary apertures have a length that
is different from the length of the primary apertures.
2. The surface mountable interdigital block filter of claim 1,
wherein the conductive material disposed on the dielectric volume
includes at least a wrap-around conductor pattern on at least the
first surface of the dielectric volume and around the input and
output secondary apertures at the first surface for facilitating
conductive connection of the surface mountable interdigital block
filter to the conductive surface of the substrate.
3. The surface mountable interdigital block filter of claim 1,
wherein the first surface and the second surface of the volume of
dielectric material are opposing surfaces and wherein each
conductive resonator means substantially comprises a resonator
whose length extends between first and second surfaces.
4. The surface mountable interdigital block filter of claim 1,
wherein the conductive material includes silver.
5. The surface mountable interdigital block filter of claim 1,
wherein said first conductive line and said second conductive line
are comprised of a first conductor pad and a second conductor pad,
respectively, and said first and second conductor pads are located
proximate to a radiating end of said input and output secondary
apertures, respectively.
6. A surface mountable interdigital block filter for utilizing
resonators for zero(s) in a frequency transfer function for
filtering electrical signals, the block filter being substantially
directly mountable on a conductive surface of a substrate,
comprising:
a substantially parallelepiped volume of dielectric material having
at least a first and a second surface substantially arranged to
provide:
three primary apertures extending coaxially from said first and
second surfaces and having conductive material disposed on an inner
surface of said apertures to provide conductive resonator
means,
input and output secondary apertures extending coaxially from said
first and second surfaces and having conductive material disposed
on an inner surface of said secondary apertures to provide
conductive resonator means, for at least facilitating external
conductive connections and at least allowing desired provision and
extraction of electrical signals,
wherein the secondary apertures are operably coupled to the primary
apertures and the apertures are arranged in an order of:
a first primary aperture, the input secondary aperture, a second
primary aperture, the output secondary aperture, and a third
primary aperture,
a first conductive line is utilized for input into the input of the
secondary aperture and a second conductive line is utilized for
output from the output secondary aperture,
wherein adjacent apertures are at least alternately connected and
unconnected to a ground respectively along the first surface and
along the second surface such that said conductive resonator means
are interdigitated; and
conductive material is disposed on at least part of the surfaces of
the volume of dielectric material, substantially arranged to at
least permit conductive surface mounting of the surface mountable
interdigital block filter on the conductive surface of the
substrate and to provide an electrical signal filter that provides
for selectable frequency rejection response operation
wherein the input and output secondary apertures are utilized,
respectively, to radiate and receive signals to and from adjacent
conductive interdigitated resonator(s) means,
wherein said conductive interdigitated resonator means are
constructed and arranged such that the block filter has at least a
first pole and at least a first zero in its frequency transfer
function provided by at least a first resonator that is utilized
for zero(s) of a frequency transfer function, and
wherein the input and output secondary apertures have a length that
is different from the length of the primary apertures.
7. The surface mountable interdigital block filter of claim 6,
wherein the conductive material disposed on the dielectric
parallelepiped includes at least a wrap-around conductor pattern on
at least the first surface of the dielectric parallelepiped and
around the input and output secondary apertures at the first
surface for facilitating conductive connection of the surface
mountable interdigital block filter to the conductive surface of
the substrate.
8. The surface mountable interdigital block filter of claim 6,
wherein the first surface and the second surface of the
parallelepiped of dielectric material are substantially opposing
surfaces and wherein each conductive resonator means substantially
comprises a resonator whose length extends between first and second
surfaces.
9. The surface mountable interdigital block filter of claim 6,
wherein the conductive material includes silver.
10. The surface mountable interdigital block filter of claim 6,
wherein said first conductive line and said second conductive line
are comprised of a first conductor pad and a second conductor pad,
respectively, and said first and second conductor pads are located
proximate to a radiating end of said input and output secondary
apertures, respectively.
11. A surface mountable interdigital block filter in a radio, for
utilizing resonators for zero(s) in a frequency transfer function
for filtering electrical signals, the block filter being
substantially directly mountable on a conductive surface of a
substrate, comprising:
a substantially parallelepiped volume of dielectric material having
at least a first and a second surface substantially arranged to
provide:
five primary apertures extending coaxially from said first and
second surfaces and having conductive material disposed on an inner
surface of said apertures to provide conductive resonator
means,
input and output secondary apertures extending coaxially from said
first and second surfaces and having conductive material disposed
on an inner surface of said secondary apertures to provide
conductive resonator means, for at least facilitating external
conductive connections and at least allowing desired provision and
extraction of electrical signals,
wherein the secondary apertures are operably coupled to the primary
apertures and the apertures are arranged in an order of:
a first primary aperture, the input secondary aperture, second,
third and fourth primary apertures, the output secondary aperture,
and a fifth primary aperture,
a first conductive line is utilized for input into the input
secondary aperture and a second conductive line is utilized for
output from the output secondary aperture,
wherein adjacent apertures are at least alternately connected and
unconnected to a ground respectively along the first surface and
along the second surface such that said conductive resonator means
are interdigitated, and
conductive material is disposed on at least part of the surfaces of
the volume of dielectric material, substantially arranged to at
least permit conductive surface mounting of the surface mountable
interdigital block filter on the conductive surface of the
substrate and to provide an electrical signal filter that provides
for selectable frequency rejection response operation
wherein the input and output secondary apertures are utilized,
respectively, to radiate and receive signals to and from adjacent
conductive interdigitated resonator(s) means,
wherein said conductive interdigitated resonator means are
constructed and arranged such that the block filter has at least a
first pole and at least two zeroes in its frequency transfer
function provided by resonators that are utilized for zero(s) of a
freauenov transfer function, and
wherein the input and output secondary apertures have a length that
is different from the length of the primary apertures.
12. The surface mountable interdigital block filter of claim 11,
wherein the conductive material disposed on the dielectric volume
includes at least a wrap-around conductor pattern on at least the
first surface of the dielectric volume and around the input and
output secondary apertures at the first surface for facilitating
conductive connection of the surface mountable interdigital block
filter to the conductive surface of the substrate.
13. The surface mountable interdigital block filter of claim 11,
wherein the first surface and the second surface of the volume of
dielectric material are opposing surfaces and wherein each
conductive resonator means substantially comprises a resonator
whose length extends between first and second surfaces.
14. The surface mountable interdigital block filter of claim 11,
wherein the conductive material includes silver.
15. The surface mountable interdigital block filter of claim 11,
wherein said first conductive line and said second conductive line
are comprised of a first conductor pad and a second conductor pad,
respectively, and said first and second conductor pads are located
proximate to a radiating end of said input and output secondary
apertures, respectively.
Description
This application is related to the application filed concurrently
herewith: Surface Mountable Interdigital Block Filter (Ser. No.
07/667,841); Truc Giang-Nguyen Hoang, Inventor; Motorola Inc.,
Assignee.
FIELD OF THE INVENTION
The present invention is generally related to electrical signal
filters, and more particularly to surface mountable block
filters.
BACKGROUND OF THE INVENTION
As mobile and portable radios and electrical devices have decreased
in size, transceivers and filters utilized therein have been
modified to be more space efficient. Surface mountable filters that
mount directly to a substrate have been utilized to reduce
electrical component space requirements. Typically, a transfer
function of a block filter component is associated with operating
characteristics of that block filter. In theory, the transfer
function typically may have a numerator with roots that are termed
zeros, and a denominator with roots that are termed poles. However,
surface mountable block filters have previously failed to include
filters having transfer functions with zeros, lacking selectable
frequency rejection response characteristics. There is a need for a
surface mountable block filter that, while utilizing a transfer
function with at least one pole, simultaneously provides for
selectable frequency rejection response operation.
SUMMARY OF THE INVENTION
A surface mountable interdigital block filter for filtering
electrical signals is provided that has at least a first pole and
at least a first zero in its frequency transfer function and that
is substantially directly mountable on a conductive surface of a
substrate, the filter comprising at least:
a volume of dielectric material having at least a first and a
second surface, substantially arranged to provide at least:
three apertures, arranged and operably coupled to substantially
provide at least:
a first conductive interdigitated resonator means, extending from
the first surface of the volume of dielectric material to the
second surface of the volume of dielectric material, utilizing a
primary aperture formed in the volume of dielectric material for
each conductive resonator, primary apertures being substantially
coaxial, extending from the first surface of the volume of
dielectric material to the second surface of the volume of
dielectric material, and each conductive resonator having
conductive material disposed on an inner peripheral surface of the
at least three primary apertures;
a conductive input unit and a conductive output unit, each operably
coupled to at least a first conductive interdigitated resonator
unit, for at least facilitating external conductive connections and
at least allowing desired provision and extraction of electrical
signals to and from selected conductive resonator means;
such that adjacent apertures substantially are at least alternately
connected and unconnected to a ground respectively along the first
surface and along the second surface; and
conductive material disposed on at least part of the surfaces of
the volume of dielectric material, substantially arranged to at
least permit conductive surface mounting of the surface mountable
interdigital block filter on the conductive surface of the
substrate and to substantially provide an electrical signal filter
that substantially provides for selectable frequency rejection
response operation.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A, 1B, and 1C, respectively, are schematics of a top view, a
side view, and a bottom view, respectively, of a first embodiment
of a surface mountable interdigital block filter in accordance with
the present invention.
FIG. 2 is a schematic of a circuit diagram of the first embodiment
of a block filter in accordance with the present invention.
FIG. 3 is a schematic perspective view of a second embodiment of a
surface mountable interdigital block filter in accordance with the
present invention.
FIG. 4 is a schematic of a circuit diagram of the second embodiment
of a block filter in accordance with the present invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
FIGS. 1A, 1B, and 1C, respectively, are schematics of a top view, a
side view, and a bottom view, respectively, of a first embodiment
of a surface mountable interdigital block filter in accordance with
the present invention, wherein the block filter utilizes at least
five conductive interdigitated resonators, each having a primary
aperture (102, 104, 106, 108, 110, . . . ). The first embodiment of
the surface mountable interdigital block filter comprises at least
a volume of dielectric material, typically a parallelepiped, having
at least a first surface (112) and a second surface (114), being
opposing surfaces in a parallelepiped, substantially arranged to
provide at least: seven apertures (102, 104, 106, 108, 110, 116,
118, . . . ), arranged and operably coupled by input and output
line tapping to substantially provide at least: five conductive
interdigitated resonators, each extending from the first surface
(112) of the volume of dielectric material to the second surface
(114) of the volume of dielectric material. Input and output line
tapping is defined substantially as conductive connection of a
first secondary aperture of a conductive input to a first primary
aperture of a resonator end, and conductive connection of a second
secondary aperture to a conductive output to a last primary
aperture of a resonator end of the filter. Interdigitated means
that adjacent resonator apertures are substantially alternately
connected to ground. Interdigitation aids in reducing undesirable
coupling between adjacent resonator apertures due to antenna-like
radiation of radio signals from aperture ends.
Each interdigitated resonator utilizes a primary aperture (102,
104, 106, 108, 110, . . . ) formed in the volume of dielectric
material for each conductive resonator, primary apertures (102,
104, 106, 108, 110 . . . ) being substantially coaxial, extending
from the first surface (112) of the volume of dielectric material
to the second surface (114) of the volume of dielectric material.
Placement of primary apertures (102, 104, 106, 108, 110, . . . ) in
the filter block and the spacing of adjacent primary apertures is
selected to obtain desired electrical filtering
characteristics.
Further, the volume of dielectric material includes at least two
secondary apertures (116, 118, . . . ), apertures that are utilized
for conductive input and conductive output, each conductive input
and output extending from the first surface (112) of the volume of
dielectric material to the second surface (114) of the volume of
dielectric material, secondary apertures further being
substantially coaxial. Each conductive input and conductive output
(116, 118, . . . ) has a conductive layer formed on an inner
peripheral surface of the at least two secondary apertures, for at
least facilitating external conductive connections, each is
operably connected to at least a first resonator, thereby allowing
desired provision and extraction of electrical signals to and from
selected conductive resonators.
Adjacent apertures substantially are at least alternately connected
and unconnected to a ground respectively along the first surface
(112) and along the second surface (114).
In the first embodiment, two zeros in the transfer function for the
block filter are substantially obtained by placing a first
conductive resonator, a conductive input secondary aperture (116),
a second conductive resonator, a third conductive resonator, a
fourth conductive resonator, a conductive output secondary aperture
(118), and a fifth conductive resonator seriatim, interdigitated,
in the volume of dielectric material, wherein a conductive
resonator for a zero (for the first embodiment, the first
conductive resonator and the fifth conductive resonator,
respectively) has a first surface conductive material pattern and a
second surface conductive material pattern that is one of: (one)
substantially the same as a first surface conductive material
pattern and a second surface material pattern of an adjacent
conductive resonator for a pole (for the first embodiment, the
second conductive resonator and the fourth conductive resonator,
respectively) and (two) substantially reversed from a first surface
conductive material pattern and a second surface conductive
material pattern of an adjacent conductive input/output secondary
aperture (for the first embodiment, the conductive input secondary
aperture and the conductive output secondary aperture,
respectively). Further zeros may be added, as desired by adding
further conductive resonators next to existing zero conductive
resonator apertures at a position away from a centermost portion of
the filter block. Conductive resonators implemented for zeros
differ from conductive resonators for poles in at least one of:
aperture diameter, aperture length, and first surface and second
surface conductor material patterns of a conductive resonator for a
zero reversed from those of a conductive resonator for a pole.
Conductive material is substantially disposed on at least part of
the surfaces of the volume of dielectric material, and is
substantially arranged, typically by a conductive material first
surface connection (122A, 124A) to the conductive input and output
overlapped to a substantially perpendicular surface (122B, 124B) to
at least permit conductive surface mounting of the surface
mountable interdigital block filter on the conductive surface of
the substrate and to substantially provide an electrical signal
filter that is selectably frequency adjustable. Selected surface
areas are typically not covered with conductive material (126A,
126B, 120, 128A, 128B, 130, 132, 134, 136) to allow input and
output connections and to aid in interdigitation.
FIG. 2 is a schematic of a circuit diagram of the first embodiment
of a block filter in accordance with the present invention, wherein
the block filter utilizes at least five conductive interdigitated
resonators, each having a primary aperture (102,104, 106,.108, 118,
110, . . . ). The first embodiment has at least 7 apertures
comprising at least five primary apertures that function as
resonators (102, 104, 106, 108, 110), and at least two secondary
apertures that function as an input and an output (116, 118).
Typical capacitances are selectable. Transmission lines (216, 218,
220, 222, 224, 226, 228) represent the seven apertures. Physically,
a permittivity (Er) of the block filter, a size of the aperture,
and a location of the aperture in the filter block define
operational characteristics of impedance (Z) for that aperture and
the frequency of operation of the filter defines a resonator
electrical length (LEN). Transmission lines (230, 232, 234, 236,
238, 240) represent an electrical coupling between adjacent
apertures. Capacitors (242, 244, 246, 248, 250, 252, 254) represent
electrical capacitances due to surface patterns of conductive
material; these surface patterns are utilized to fine tune an
operating frequency of the filter block, typically up or down by at
least 100 MHz. Typical values for such capacitances (242, 244, 246,
248, 250, 252, 254) are usually less than 1.5 pF.
For example, a workable set of operational characteristics for a
surface mountable interdigital block filter in accordance with the
present invention is substantially: a substantially
rectangular-sided parallelepiped, substantially 4.826
cm..times.0.5334 cm..times.height cm. (1.900 in..times.0.210
in..times.height in.) (LEN of resonators, height being frequency
dependent) of dielectric material (Er substantially 37.3) having
aperture spacing, as one approaches a center of a first surface of
the volume of dielectric material from two opposing outer edges of
the first surface, of edge to first aperture center of
substantially 0.3556 centimeters (cm.) (0.14 inches (in.)),
aperture center to aperture center of substantially 0.5461 cm.
(0.215 in) for conductive input and output apertures to adjacent
resonator aperture center, and aperture center to aperture center
of substantially 0.6223 cm. (0.245 in.) for a next adjacent
resonator aperture center to adjacent resonator aperture center,
next adjacent resonator aperture center to adjacent resonator
aperture center spacing of substantially 0.889 cm. (0.35 in), and
substantially having capacitances (in pF) and impedances (in
ohms):
14.52 ohms at a first aperture transmission line (216);
13.32 ohms at a second aperture transmission line (218);
12.54 ohms at a third aperture transmission line (220);
12.28 ohms at a fourth aperture transmission line (222);
12.54 ohms at a fifth aperture transmission line (224);
13.32 ohms at a fifth aperture transmission line (226);
14.52 ohms at a fifth aperture transmission line (228);
215.5 ohms at a first adjacent aperture coupling transmission line
(230);
293.98 ohms at a second adjacent aperture coupling transmission
line (232);
1419.32 ohms at a third adjacent aperture coupling transmission
line (234);
1419.32 ohms at a fourth adjacent aperture coupling transmission
line (236);
293.98 ohms at a third adjacent aperture coupling transmission line
(238);
215.5 ohms at a fourth adjacent aperture coupling transmission line
(240);
0.8 pF at a first surface pattern capacitance (242);
1.1 pF at a second surface pattern capacitance (244);
0.9 pF at a third surface pattern capacitance (246);
0.9 pF at a fourth surface pattern capacitance (248);
0.9 pF at a fifth surface pattern capacitance (250);
1.1 pF at a fourth surface pattern capacitance (252); and
0.8 pF at a fifth surface pattern capacitance (254).
FIG. 3 is is a schematic perspective view of a second embodiment of
a surface mountable interdigital block filter in accordance with
the present invention, wherein capacitive conductive tapping is
utilized for conductive input and conductive output. The second
embodiment of the surface mountable interdigital block filter
comprises at least a volume of dielectric material, typically a
parallelepiped, having at least a first surface (302) and a second
surface (304), being opposing surfaces in a parallelepiped,
substantially arranged to provide at least: five apertures (306,
308, 310, 312, 314, . . . ), arranged and operably coupled by
capacitive tapping, to substantially provide at least: five
conductive interdigitated resonators, each extending from the first
surface (302) of the volume of dielectric material to the second
surface (304) of the volume of dielectric material. Capacitive
tapping is defined substantially as placing a first conductor pad
for input near a radiating end of a first primary aperture of a
resonator and a second conductor pad for output near a radiating
end of a second primary aperture of a last resonator for input and
output connection. Each interdigitated resonator utilizes a primary
aperture (306, 310, 314, . . . ) formed in the volume of dielectric
material for each conductive resonator, primary apertures (306,
310, 314, . . . ) being substantially coaxial, extending from the
first surface (302) of the volume of dielectric material to the
second surface (304) of the volume of dielectric material.
Placement of primary apertures (306, 310, 314, . . . ) in the
filter block and the spacing of adjacent primary apertures is
selected to obtain desired electrical filtering
characteristics.
Further, the volume of dielectric material includes at least two
secondary apertures (308, 312, . . . ), apertures that are utilized
for conductive input and conductive output, each conductive input
and output extending from the first surface (302) of the volume of
dielectric material to the second surface (304) of the volume of
dielectric material, secondary apertures further being
substantially coaxial. Each conductive input and conductive output
aperture (308, 312 . . . ) has a conductive layer formed on an
inner peripheral surface of the at least two secondary apertures,
for at least facilitating external conductive connections, each is
operably connected by capacitive tapping to at least a first
resonator, thereby allowing desired provision and extraction of
electrical signals to and from selected conductive resonators.
Adjacent apertures substantially are at least alternately connected
and unconnected to a ground respectively along the first surface
(302) and along the second surface (304).
In the second embodiment, two zeros in the transfer function for
the block filter are substantially obtained by placing a first
conductive resonator, a conductive input secondary aperture (308),
a second conductive resonator, a conductive output secondary
aperture (312), and a third conductive resonator seriatim,
interdigitated, in the volume of dielectric material, wherein
conductive resonators implemented for zeros differ from conductive
resonators for poles in at least one of: aperture diameter,
aperture length, and first surface and second surface conductor
material patterns of a conductive resonator for a zero reversed
from those of a conductive resonator for a pole, and wherein a
conductive resonator for a zero (for the second embodiment, the
first conductive resonator and the third conductive resonator,
respectively) has a first surface conductive material pattern and a
second surface conductive material pattern that is one of: (one)
substantially the same as a first surface conductive material
pattern and a second surface material pattern of an adjacent
conductive resonator for a pole (for the second embodiment, the
second conductive resonator) and (two) substantially reversed from
a first surface conductive material pattern and a second surface
conductive material pattern of an adjacent conductive input/output
secondary aperture (for the second embodiment, the conductive input
secondary aperture and the conductive output secondary aperture,
respectively). Further zeros may be added, as desired by adding
further conductive resonators next to existing zero conductive
resonator apertures at a position away from a centermost portion of
the filter block. Conductive resonators implemented for zeros
differ from conductive resonators for poles in at least one of:
aperture diameter, aperture length, and first surface and second
surface conductor material patterns of a conductive resonator for a
zero reversed from those of a conductive resonator for a pole.
Conductive material is substantially disposed as described for the
first embodiment.
FIG. 4 is a schematic of a circuit diagram of the second embodiment
of a block filter in accordance with the present invention, wherein
the block filter utilizes at least three conductive interdigitated
resonators, each having a primary aperture (306, 310, 314, . . . ).
The second embodiment has at least 5 apertures (306, 308, 310, 312,
314, . . . ) comprising at least three primary apertures that
function as resonators (306, 310, 314), and at least two secondary
apertures that function as an input and an output (308, 312, . . .
). Typical capacitances are selectable. Transmission lines (416,
418, 420, 422, 424) represent the five apertures. Physically, a
permittivity (Er) of the block filter, a size of the aperture, and
a location of the aperture in the filter block define operational
characteristics of impedance (Z) for that aperture and the
frequency of operation of the filter defines a resonator electrical
length (LEN). Transmission lines (426, 428, 430, 432) represent an
electrical coupling between adjacent apertures. Capacitors (444,
446, 448, 450) represent capacitances due to input and output
connections, respectively. Capacitors (434, 436, 438, 440, 442)
represent electrical capacitances due to surface patterns of
conductive material; these surface patterns are utilized to fine
tune an operating frequency of the filter block, typically up or
down by at least 100 MHz. Typical values for such surface pattern
capacitances (434, 436, 438, 440, 442) are usually less than 1.5
pF.
The present invention provides a surface mountable interdigital
block filter that provides for selectable frequency rejection
response operation in a compact unit, thereby facilitating
construction of smaller devices, such as radios, that utilize
electrical signal filters.
* * * * *